Coating composition and method for the improvement of surface hardness of article by the use thereof

A coating composition consisting essentially of:

• (A) 100 parts by weight of partially hydrolyzed silicon compounds consisting essentially of co-partial hydrolyzates of a tetraalkoxysilane of the formula (Si(OR.sup.1).sub.4 wherein R.sup.1 is an alkyl having 1 to 4 carbon atoms and an organic silicon compound of the formula:
• R.sub.n.sup.2 Si(OR.sup.3).sub.4-n wherein n is an integer of from 1 to 3, R.sup.2 is a hydrocarbon group having 1 to 6 carbon atoms and R.sup.3 is an alkyl having 1 to 4 carbon atoms and/or a mixture of partial hydrolyzates of each tetraalkoxysilane and organic silicon compound, said partially hydrolyzed silicon compounds containing said partially hydrolyzed tetraalkoxysilane, calculated as SiO.sub.2, and said organic partially hydrolyzed silicon compound, calculated as R.sub.n.sup.2 SiO.sub.m wherein m=(4-n)/2, in the ratio of 5/95 to 95/5 by weight, and the weight (100 parts by weight) of said partially hydrolyzed silicon compounds being also calculated as SiO.sub.2 for said partially hydrolyzed tetraalkoxysilane and as R.sub.n.sup.2 SiO.sub.m for said partially hydrolyzed organic silicon compound,
• (B) 10 to 400 parts by weight of a monomer or oligomer having two or more hydroxy groups, and
• (C) 0 to 300 parts by weight of an etherified methylolmelamine, wherein said etherified methylolmelamine is contained in an amount of 0.5 to 1.5 gram equivalent per 1 gram equivalent of the monomer or oligomer, said composition being dissolved in a solvent.